package main

import "fmt"

/*
Given an array arr of integers, check if there exists two integers N and M such that N is the double of M ( i.e. N = 2 * M).
More formally check if there exists two indices i and j such that :
i != j
0 <= i, j < arr.length
arr[i] == 2 * arr[j]

Example 1:
Input: arr = [10,2,5,3]
Output: true
Explanation: N = 10 is the double of M = 5,that is, 10 = 2 * 5.

Example 2:
Input: arr = [7,1,14,11]
Output: true
Explanation: N = 14 is the double of M = 7,that is, 14 = 2 * 7.

Example 3:
Input: arr = [3,1,7,11]
Output: false
Explanation: In this case does not exist N and M, such that N = 2 * M.

Constraints:
2 <= arr.length <= 500
-10^3 <= arr[i] <= 10^3
*/

func main() {
	fmt.Println(checkIfExist([]int{10, 2, 5, 3}))
	fmt.Println(checkIfExist([]int{7, 1, 14, 11}))
	fmt.Println(checkIfExist([]int{3, 1, 7, 11}))
}

func checkIfExist(arr []int) bool {
	dict := make(map[int]int, len(arr))

	for idx, v := range arr {
		dict[v] = idx
	}

	for idx, v := range arr {
		if dict_idx, ok := dict[v+v]; ok && idx != dict_idx {
			return true
		}
	}

	return false
}
